Nontarnishing detergent compositions containing stannous salts



United States Patent NONTARNISHING DETERGENT COMPOSITIONS CONTAININGSTANNOUS SALTS Edgar E. Ruff, Bergenfield, and Elwin E. Smith, Paramus,N.J., assignors to Lever Brothers Company, New York, N.Y., a corporationof Maine No Drawing. Application August 16, 1955 Serial No. 528,814

16 Claims. (Cl. 252-135) This invention relates to detergentcompositions containing tarnish inhibitors and more particularly topolyphosphate compositions containing water-soluble stannous salts astarnish inhibitors.

Compositions containing polyphosphates are now widely used for detergentand other purposes. Aqueous solutions of polyphosphates tend, when atcertain pH values to tarnish copper, and nickel and copper alloys suchas German silver (a nickel-zinc-copper alloy) to a variety of shadesfrom yellow to bluish-black, especially if the solutions are at elevatedtemperatures and are allowed to remain in contact with the metal oralloy for several minutes. Since German silver is frequently used forhousehold articles commonly washed in polyphosphatebuilt detergentcompositions, it is evident that this is a serious problem.

In accordance with the instant invention polyphosphate compositions areprovided containing a tarnish inhibitor which compositions inhibit theformation of tarnish upon copper, and nickel and copper alloys such asGerman silver. The tarnish inhibitors of the invention are watersolubleinorganic and organic stannous salts, for example, stannous chloride,bromide, fluoride, tartrate, iodide, and sulfate. Stannic salts on theother hand are inefiective to inhibit the formation of tarnish.

It has not been possible to determine the exact form of the tincompounds present in washing solutions of the detergent compositions dueto the complexity of the system. water-soluble stannous salt may beconverted into a stannite or a soluble tin-polyphosphate complex. Forthe sake of clarity, therefore, the tarnish inhibitors are referred toas water-soluble stannous salts, especially since on a production basisthe tarnish inhibitors are added to the crutcher slurry of the detergentproduct in the form of water-soluble stannous salts.

An amount of the water-soluble stannous salt is added to thepolyphosphate composition which is sufiicient to give tarnish inhibitionwhen the composition is used in. its normal way. It will be understoodthat the amount required will depend in part upon the tarnish inhibitingproperties of the particular stannous salt in question, upon thetendency of the polyphosphate with which it is used to tarnish copper,and nickel and copper alloys, and upon the amount of polyphosphatepresent. In general, therefore, at least about 1.3% of the water-solublestannous salt based on the weight of the polyphosphate present in thedetergent composition will inhibit the formation of tarnish by thecomposition. The maximum amount of the stannous salt is not critical,but more than is necessary to give the desired effect will usually notbe used, and of course an amount in excess of that soluble in an aqueoussolution of the composition would not be used. In most cases, themaximum suggested would be about 6.7%.

The tarnish inhibitors of the present invention are effective withwater-soluble alkali metal polyphosphates It is believed that a minorproportion of the.

at pH values where such polyphosphates tend to tarnish German silver,i.e., usually within the range of about pH 7 to about pH 11. The alkalimetal polyphosphates may include, by way of example, pentasodium andpentapotassium tripolyphosphates, tetrasodium and tetrapotassiumpyrophosphates, sodium and potassium hexametaphosphates, and hexasodiumand hexapotassium tetrapolyphosphates. There is no critical amount ofalkali metal polyphosphate which need be employed in the compositions,the amount of polyphosphate in the compositions being dictated only bythe optional presence of organic nonsoap detergents and builders whichmight be included in the detergent compositions.

Examples of such additional optional components are organic nonsoapdetergents which may be either anionic, cationic, or nonionic detergentsand builders, water, and inert materials. These detergent compositionsmay contain alkali metal polyphosphate in any amount, usually between 5%and conventional proportions of organic nonsoap detergent, usuallywithin the range between 5% and 40%; at least about 1.3% of awatersoluble stannous salt based on the weight of the polyphosphate; andthe balance builders and inert materials.

The alkylaryl sulfonates are a class of anionic detergents which may beincluded in the detergent compositions. One example thereof is thesulfonated phenyl polypropylene alkanes, characterized by the branchedchain structure of polypropylene and a tertiary alkyl carbon at thebenzene ring, and having the following general structure:

where M is hydrogen, an alkali metal or an organic amine amidoalkanesulfonates which are characterized by the following structure:

R-0 o-N-(oHnnsoaa Where A is hydrogen or alkali metal, i.e., ammonium,sodlum, or potassium, n is a small whole number from one to Thesecompounds are prepared by interacting the corresponding aliphatic acidanhydride or halide with an organic aliphatic aminosulfonic acid, suchas taurine, NH CH CH SO H, and the various N-substituted taurines, suchas N-methyl taurine, or aminopropane sulfonic Other water-soluble alkylaromatic sulfonic acids may constitute optional components such as thoseprepared by alkylating benzene or naphthalene with a kerosene fractionfollowed by sulfonation of aliphatic sulfonic acids, esters of sulfuricacid with aliphatic alcohols of ten Patented Sept. 8, 1959 to eighteencarbon atoms, particularly those derived by the reduction of coconutoil, palm oil and like long-chain fatty acids, sulfonated castor oil,esters and ethers of isethionic acid, long-chain fatty acid esters andlong-chain alkyl ethers of 2,3-dihydroxypropane sulfonic acid andsulfuric acid esters of monoglycerides and glycerol mono others. Thesalts of these acids are ordinarily employed. The tarnish inhibitors arealso useful with nonionic detergents containing polyphosphates, such as,for example, alkyl oxyether and ester and thioether and est r.detergents having the following general formula:

where R is a straight or branched chain saturated or unsaturatedhydrocarbon group having from eight to eighteen carbon atoms or anaralkyl group having a straight or branched chain saturated orunsaturated hydrocarbon group of from eight to eighteen carbon atomsattached to the aryl nucleus, and attached to A through the arylnucleus, A is selected from the group consisting of ethereal oxygen andsulfur, carboxylic ester and thiocarboxylic ester groups and x is anumber from eight to twenty. R can, for example, be a straight orbranched chain octyl, nonyl, decyl, lauryl, myristyl, cetyl or stearylgroup, or an alkyl aryl group such as octylbenzene, nonylbenzene,decylbenzene, stearylbenzene, etc.

' The sulfated ethoxynated derivatives of the above also are usefulanionic detergents:

where M is hydrogen or an alkali metal or organic amine cation and x, Aand R are as above.

When R is alkyl it will be evident that the detergent can be regarded asderived from an alcohol, mercaptan, oxy or thio fatty acid of highmolecular weight, by condensation with ethylene oxide. Typical of thistype of alkyl ether are the condensation products of oleyl or dodecylalcohol or mercaptan with from eight to seventeen moles of ethyleneoxide, such as Emulfor ON, Nonic 218 and Sterox SE and SK. Typical alkylesters are G1226 and Renex (polyoxyethylene ester of tall oil acids),Sterox CD and Neutronyx 330 and 331 (higher fatty acid esters ofpolyethylene glycol).

Where R is aralkyl, the detergent can be derived from an alkyl phenol orthiophenol.

The ethoxynated alkyl phenols and thiophenols have the following generalformula:

aonicrnohcntomon where R is a straight or branched chain saturated orunsaturated hydrocarbon group having at least eight carbon atoms up toapproximately eighteen carbon atoms, A is oxygen or sulfur and x is anumber from eight to twenty. R can, for example, be a straight orbranched chain octyl, nonyl, decyl, lauryl, cetyl, myristyl or stearylgroup. Typical are the condensation products of octyl and nonyl phenoland thiophenol with from eight to seventeen moles of ethylene oxide,available commercially under the trade names NIW, Antarox A400, IgepalCA and CO, Triton X-100, Neutronyx 600 and Tergitol NFX.

The optional supplemental builders may be alkali metal inorganic salts,typical examples of which include sodium and potassium sulfates, sodiumand potassium chlorides, sodium and potassium silicates, and sodium andpotassium carbonates.

' In addition to or instead of the above mentioned supplementalinorganic salts, organic materials such as sodium carboxymethylcellulose can be used as builders.

The builder mixture is so chosen among alkaline, neutral, and acidicsalts that the composition obtained in an aqueous 0.14% washing solutionhas a pH of about 7 or above. Preferably its pH lies within the range ofabout 7 to about 11, since solutions which are more alkaline may beirritating to the skin and tend to weaken some fabrics, particularlywoolens. In general, the alkali metal carbonates are preferred agentsfor bringing the pH of the solution to a high alkaline value within thepreferred range.

The detergent compositions of the invention inhibit the formation oftarnish upon copper, and nickel and copper alloys such as German silverin either hard or soft water. It will be appreciated that the detergentcompositions may exist in any dry form, such as drum-dried or spraydrieddetergent compositions, or may be in liquid form.

The polyphosphate detergent compositions may be prepared by conventionalmethods, as by blending the ingredients thereof in an aqueous solutionor slurry and then drying the resulting mixture in a spray or drum 170F. to provide 2.25 grams of polyphosphate per quart of solution. Atarnish inhibitor was then added thereto in the form of a solution. Morewater was then added thereto to give a total volume of one quart. 300mls. of the solution were placed in a beaker and the temperatureadjusted to F. to F. A strip of metal, such as.

German silver, six inches by one inch which had been cleaned with ametal polish and rinsed and dried was partially immersed in the solutionand allowed to remain for one-half hour at 160 F. to 170 F. The metalstrip was then removed, rinsed and dried with a cloth. The strip wasvisually examined for tarnish and the effectiveness of the tarnishinhibitor rated as follows:

Grade No. Degree of Tarnish No tarnish.

Interface stain only.

Barely noticeable tarnish.

Slight tarnish.

Moderate tarnish.

Considerable (heavy) tarnish. Severe, as when inhibitor is absent.

Examples 1-18 below show that at least about 3% of a water-solublestannous salt based on the weight of polyphosphate inhibits theformation of tarnish by typical polyphosphates, such as pentasodiumtripolyphosphate, tetrasodium pyrophosphate, sodium hexametaphosphate,and hexasodium tetrapolyphosphate. More specifically, the examples showthat at least about 3% of stannous chloride based on the weight ofpolyphosphate is effective in inhibiting the formation of tarnish bypentasodium tripolyphosphate and tetrasodium pyrophosphate, while atleast about 0.3% of stannous chloride is effective in inhibiting theformation of tarnish by sodium hexametaphosphate. and at least about 1%of stannous chloride is effective in inhibiting the formation of tarnishby hexasodium tetrapolyphosphate.

EXAMPLES 1-18 To separate 225 gram portions of the four polyphos phateslisted below dissolved in distilled water-were added varying proportionsof stannous chloride, and the volume diluted to one quart in accordancewith the above test Percent stannous Chloride (polyphosphate basis) 0.30.6 1.1 2.2 3.3 4.4

Polyphosphate Tarnish Grade Pentasodium Tripolyphosphate (Examples 1-5)6 6 4 3 Tetrasodium Pyrophosphate (Examples 6-10) 6 5 5 2 2 SodiumHexametaphosphate (Examples 11-15) 6 3 2 2 1 HexasodiumTetrapolyphosphate (Examples 16-18) 6 4 2 A water-soluble stannous saltis effective as a tarnish inhibitor in polyphosphate compositions whichcontain EXAMPLES 19-22 0.9 gram of sodium dodecylbenzenesulfonate and2.25 grams of pentasodium tripolyphosphate were dissolved in distilledwater, and 4.4% of stannous chloride based on the weight of thepolyphosphate added thereto, and the solution diluted to a volume of onequart. This solution tarnished German silver only to grade 1 while anidentical solution without the presence of the stannous chloridetarnished German silver to grade 6. Tetra sodium pyrophosphate wassubstituted in the same amount for the pentasodium tripolyphosphate inthe above composition. A strip of German silver metal placed in thesolution of the composition containing stannous chloride was tarnishedonly to grade 1, whereas a strip of German silver metal placed in thesolution of the composition without the presence of the stannouschloride tarnished to grade 6.

The addition of a water-soluble stannous salt to polyphosphatecompositions containing an organic nonsoap detergent, which may beeither anionic, nonionic, or cationic, as well as supplemental buildersinhibits the formation of tarnish by such detergent compositions. Thisis clearly illustrated by the examples set forth below wherein thefollowing two compositions, or specified modifications thereof, wereemployed.

In compositions X and Y the amounts of the various components areexpressed in percent by Weight.

EXAMPLES 23-34 To 5 grams each of compositions X and Y there was addedstannous chloride in the proportions shown below and the test procedurecarried out with the following results.

Percent stannous Chloride,

Polyphosphate Basis 0 1.1 1.3 1.7 2.2 6.7

Grading (Composition X) (Examples 23-28) 6 6 4 2 1 1 Grading(Composition Y) (Examples 29-34) 6 4 4 3 3 1 Examples 23-34 show that atleast about 1.3% of stannous chloride based on the weight ofpolyphosphate inhibits the formation of tarnish by polyphosphate comanorganic nonsoap detergent as shown by Examples 19- positions containingan organic anionic nonsoap detergent EXAMPLES 35-38 Sodiumhexametaphosphate and hexasodium tetrapolyphosphate were eachsubstituted for the same amount of tetrasodium pyrophosphate incomposition X and the compositions tested in accordance with the testprocedure. 5 grams of each of these compositions in a quart of watertarnished German silver to a grading of 6, i.e., severe tarnish. When4.4% of stannous chloride based on the weight of polyphosphate was addedto each of these compositions, the tarnish grading of both compositionsupon German silver was reduced to grade 1, indicating interface stainonly.

A stannous salt is also eifective as a tarnish inhibitor inpolyphosphate compositions containing other organic anionic nonsoapdetergents as well as supplemental builders as shown by Examples 39-42.

EXAMPLES 3 9-42 The organic anionic nonsoap detergents, the sodium saltof N-palmitoyl-N-methyl taurine and sodium-3-dodecyloxy-Z-hydroxypropanesulfonate, were substituted separately for the same amount of sodiumdodecylbenzenc-sulfonate in composition X. When 5 grams of each of thesecompositions was tested in accordance with the test procedure, bothcompositions tarnished German silver to grade 6, indicating severetarnish. The tarnish was reduced to grade 4 when 2.2% of stannouschloride based on the weight of polyphosphate was included in thecomposition containing the sodium salt of N-palmitoyl- N-methyl taurine,while the tarnish was reduced to grade 2 when 2.2% of stannous chloridebased on the weight of polyphosphate was included in the compositioncontaining sodium-3-dodecyloxy-Z-hydroxypropane sulfonate.

A water-soluble stannous salt is also effective as a tarnish inhibitorin polyphosphate compositions containing either an organic cationicnonsoap detergent or an or-., ganic nonionic nonsoap detergent as wellas supplemental" builders, as illustrated by Examples 43-46.

EXAMPLES 43-46 I 18% of an organic cationic nonsoap detergent, name- 2 4)a( 3 6 )b( 2 4 )c prepared by condensing ethylene oxide with ahydrophobic base formed by the condensation of propylene.

oxide with propylene glycol where b is an integer selected from thegroup consisting of 26 to 30 and a plus 0 is an integer such that themolecule contains from 40% to 50% of ethylene oxide, was substituted forthe sodium 'dodecylbenzenesulfonate in composition X. 5 grams of each ofthese compositions when dissolved in one quart of water and tested inaccordance with the test procedure tarnished German silver to grade 6.When 2.2% of stannous chloride based on the weight of polyphosphate wasadded to each of these compositions, they both then had a tarnishgrading of 4, thereby showing a considerable improvement.

The amount of the organic nonsoap detergent present" in thepolyphosphate composition may be varied Within the range from about 5%to about 40% as noted above and as further illustrated by Examples47-50.

EXAMPLES 47-48 The following composition was prepared having a highdetergent content:

Composition Percent by Weight Sodium Dodecylbenzenesulfonate- 40.0Tetrasodium Pyrophosphate 45. Sodium Carbonate 3.0 Sodium Silicate 6.0Sodium Carboxymethylceflulose 0. Water. 5. 5

Total 100 When 5 grams of this composition was tested in accordance withthe test procedure upon German silver metal the metal had a tarnishgrade of 6. When 1.7% of stannous chloride based on the Weight ofpolyphosphate was added to the above composition, the compositiontarnished German silver only to grade 3.

The water-soluble stannous salts are effective as tarnish inhibitorswhen incorporated in a detergent-poly phosphate slurry and the slurrydrum-dried as shown by the following example.

EXAMPLE 51 The composition shown below was prepared in the form of anaqueous slurry having a 30% water content and drum-dried. 5 grams of thedrum-dried product per quart of distilled water tarnished German silveronly to grade 1.

Percent by Composition Weight Sodium Dodecylbenzenesulfonate" 18. OTetrasodium Pyrophosphate 45.0 Sodium silicate 6.0 SodiumCarboxymethylcellulose. 0.5 Stannous Chloride 1 1. 0 Sodium Sulfate andMiscellaneous Inert l\laterials 29. 5 Water 2.0

Total 100 1 Percent stannous chloride based on polyphosphate 2.2%.

Examples 52-53 illustrate the fact that the stannous salts are effectiveas tarnish inhibitors in polyphosphate compositions when thepolyphosphate compositions are used in hard water. It will be noted thatin all of the previous examples the water was soft water, i.e.,distilled water.

EXAMPLES 52-53 5 grams of composition X dissolved in a quart of waterhaving a hardness of 180 p.p.m. tarnished German silver to grade 6,whereas 5 grams of composition X containing 2.2% of stannous chloridebased on the weight of polyphosphate dissolved in a quart of waterhaving a hardness of 180 ppm. tarnished German silver only to grade 2.

The effectiveness of water-soluble stannous salts as tarnish inhibitorswith liquid polyphosphate detergent compositions is clearly illustratedin Examples 54-57.

EXAMPLES 54-57 Composition Percent by Weight PotassiumDodecylbenzenesulfonate- 10.0 Sodium Xylenesulfonate. 7. 6 LaurieIsopropanolamide. 3. 2 Laurie Diethanolamide. 3. 8 TetrapotassiumPyrophcsphata- 20.0 Sodium Silicate 7.0 Water 48. 4

Total T able 1 Stannous Chloride, 3.3% Metal or Alloy by weight based onpolyphosph ate Brass (alloy of copper and zinc) Coinage Nickel (alloy ofnickel and copper)..-

Humto Copper Monel (alloy of nickel, copper, manganese and iron) Theresults of the test show that a stannous salt is highly effective ininhibiting the formation of tarnish upon brass, coinage nickel, andMonel, and is moderately eifective in inhibiting the formation oftarnish upon copper.

Many modifications and variations may be made in the invention hereinset forth without departing from the spirit and scope thereof and onlysuch limitations should be imposed as are indicated in the appendedclaims.

We claim:

1. The process of cleaning articles formed of copper and copper andnickel alloys without imparting appreciable tarnish thereto whichcomprises washing said articles with a detergent composition consistingessentially of an alkali metal polyphosphate which in aqueous solutionhaving a pH of from about 7 to about 11 tarnishes copper and copper andnickel alloys and a water soluble stannous salt in an amount to lessenthe tarnishing action of the polyphosphate.

2. The process as set forth in claim 1 wherein the detergent compositioncontains at least about 3% by weight of the stannous salt based on theweight of the polyphosphate present in the composition.

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3. The process as set forth in claim 1 wherein the water-solublestannous salt is stannous chloride.

4. The process as set forth in claim 1 wherein the alkali metalpolyphosphate istetrasodium pyrophosphate.

5. The process as set forth in claim 1 wherein the alkali metalpolyphosphate is sodium hexametaphosphate.

6. The process as set forth in claim 1 wherein the alkali metalpolyphosphate is hexasodium tetrapolyphosphate.

7. The process as set forth in claim 1 wherein the alkali metalpolyphosphate is pentasodium tripolyphosphate.

8. The process of cleaning articles formed of copper and copper andnickel alloys without imparting appreciable tarnish thereto whichcomprises washing said articles with a detergent composition consistingessentially of from about 5% to about 50% of an alkali metalpolyphosphate which in aqueous solution having a pH of from about 7 toabout 11 tarnishes copper and copper and nickel alloys, from about 5% toabout 40% of an organic nonsoap detergent, and a water-soluble stannoussalt in an amount of at least about 1.3% based on the weight of thepolyphosphate and suflicient to inhibit such tarnishing.

9. The process as set forth in claim 8 wherein the alkali metalpolyphosphate is pentasodium tripolyphosphate.

10. The process as set forth in claim 8 wherein the alkali metalpolyphosphate is tetrasodium pyrophosphate.

11. The process as set forth in claim 8 wherein the alkali metalpolyphosphate is sodium hexametaphosphate.

12. The process as set forth in claim 8 wherein the alkali metalpolyphosphate is hexasodium tetrapolyphosphate.

13. The process as set forth in claim 8 wherein the Water-solublestannous salt is stannous chloride.

14. The process as set forth in claim 8 wherein the organic nonsoapdetergent is an organic cationic nonsoap detergent.

15. The process as set forth in claim 8 wherein the organic nonsoapdetergent is an organic nonionic nonsoap detergent.

16. The process as set forth in claim 8 wherein the organic nonsoapdetergent is an organic anionic nonsoap detergent.

References Cited in the file of this patent UNITED STATES PATENTS2,425,907 Wegst Aug. 19, 1947 2,618,603 Schaeifer Nov. 18, 19522,618,604 Schaefier Nov. 18, 1952 2,759,891 Rohrback Aug. 21, 19562,764,242 Rohrback Sept. 25, 1956 FOREIGN PATENTS 390,249 Great BritainApr. 6, 1933

1. THE PROCESS OF CLEANING ARTICLES FORMED OF COPPER AND COPPER ANDNICKEL ALLOYS WITHOUT IMPARTING APPRECIABLE TARNISH THERETO WHICHCOMPRISES WASHING SAID ARTICLES WITH A DETERGENT COMPOSITION CONSISTINGESSENTIALLY OFAN ALKALI METAL POLYPHOSPHATE WHICH IN AQUEOUS SOLUTIONHAVING A PH OF FROM ABOUT 7 TO ABOUT 11 TARNISHES COPPER AND COPPER ANDNICKEL ALLOYS AND A WATER SOLUBLE STANNOUS SALT IN AMOUNT TO LESSEN THETARNISHING ACTION OF THE POLYPHOSPHATE.